<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    body {
      margin: 0;
      height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
      background-color: #50C1E9;
    }

    .radar {
      width: 9.5em;
      height: 9.5em;
      position: relative;
      font-size: 30px;
      background-color: black;
      border-radius: 50%;
      background-image: 
        linear-gradient(
          90deg,
          transparent 49.75%,
          darkgreen 49.75%,
          darkgreen 50.25%,
          transparent 50.25%
        ),
        linear-gradient(
          transparent 49.75%,
          darkgreen 49.75%,
          darkgreen 50.25%,
          transparent 50.25%
        ),
        repeating-radial-gradient(
          transparent 0,
          transparent 0.95em,
          darkgreen 0.95em,
          darkgreen 1em,
          transparent 1em
        );
    }

    .radar::before {
      content: "";
      position: absolute;
      top: calc(1.5em / 2);
      left: calc(1.5em / 2);
      width: calc(8em / 2);
      height: calc(8em / 2);
      background: linear-gradient(
        45deg,
        rgba(0, 0, 0, 0) 50%,
        rgba(0, 192, 0, 1) 100%
      );
      border-radius: 100% 0 0 0;
      animation: scaning 5s linear infinite;
      transform-origin: right bottom;
    }

    @keyframes scaning {
      to {
        transform: rotate(1turn);
      }
    }

  </style>
</head>
<body>
  <h1 style="text-align: center; color: green">雷达</h1>
  <figure class="radar"></figure>
</body>
</html>